820  
FXUS06 KWBC 302040  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST THU NOVEMBER 30 2017  
 
6-10 DAY OUTLOOK FOR DEC 06 - 10 2017  
 
TODAY'S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE EXPECTED BROAD  
SCALE 500-HPA CIRCULATION PATTERN WITH A HIGH AMPLITUDE RIDGE ESTABLISHED ALONG  
THE WEST COAST AND AN AMPLIFYING TROUGH OVER EAST-CENTRAL NORTH AMERICA. ABOVE  
NORMAL 500-HPA HEIGHTS ARE PREDICTED OVER ALASKA AND THE WEST HALF OF THE  
CONUS. BELOW NORMAL 500-HPA HEIGHTS ARE FORECAST FOR MOST PARTS OF THE  
REMAINDER OF THE CONUS. THE GREATEST WEIGHT FOR THE BLENDED HEIGHT FORECAST WAS  
GIVEN TO TODAY'S 00Z ECMWF ENSEMBLE MEAN, BASED ON CONSIDERATION OF RECENT  
SKILL.  
 
BELOW NORMAL TEMPERATURES ARE FAVORED FOR THE NORTHERN PARTS OF THE NORTHERN  
INTERMOUNTAIN WEST, DUE TO ANOMALOUS NORTHERLY FLOW AHEAD OF A PREDICTED STRONG  
RIDGE OVER THE ALASKA PANHANDLE AREA. BELOW NORMAL TEMPERATURES ARE LIKELY FOR  
LARGE PARTS OF THE EASTERN TWO THIRDS OF THE CONUS, UNDERNEATH A PREDICTED  
STRONG ANOMALOUS TROUGH THERE. SOUTHEASTERLY FLOW LEADS TO INCREASED CHANCES OF  
ABOVE NORMAL TEMPERATURES ACROSS SOUTHERN CALIFORNIA, WHILE SURFACE HIGH  
PRESSURE AND ASSOCIATED LOW-LEVEL INVERSIONS MAY SLOW ANY WARMING TREND ACROSS  
THE INTERIOR WEST. THE PREDICTED ANOMALOUS TROUGH OVER THE SOUTHERN ALEUTIANS  
AND THE NORTH PACIFIC ENHANCES CHANCES OF ABOVE NORMAL TEMPERATURES FOR  
MAINLAND ALASKA AND THE ALASKA PANHANDLE.  
 
EARLY IN THE PERIOD, AN UPPER-LEVEL TROUGH, ALONG WITH EXPECTED UPSLOPE FLOW,  
ENHANCES ODDS OF ABOVE NORMAL PRECIPITATION ACROSS THE SOUTHERN GREAT PLAINS.  
ABOVE NORMAL PRECIPITATION IS FAVORED FROM THE SOUTHEAST U.S. TOWARD THE  
NORTHEAST AND PARTS OF THE GREAT LAKES, DUE TO FRONTAL ACTIVITIES IN THESE  
REGIONS. VERY HIGH PROBABILITIES OF BELOW NORMAL PRECIPITATION ACROSS NORTHERN  
CALIFORNIA AND THE PACIFIC NORTHWEST, AND BELOW NORMAL PRECIPITATION OVER THE  
MIDDLE MISSISSIPPI VALLEY AND SOUTHERN PARTS OF THE UPPER MISSISSIPPI VALLEY,  
ARE SUPPORTED BY THE STRONG ANOMALOUS RIDGE FORECAST ALONG THE WEST COAST AND  
VARIOUS PRECIPITATION TOOLS. AN UPPER-LEVEL TROUGH PREDICTED OVER THE ALEUTIANS  
AND SOUTHWESTERLY FLOW AT THE SURFACE INCREASE CHANCES OF ABOVE NORMAL  
PRECIPITATION THROUGHOUT MUCH OF ALASKA.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 8, 10% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 8, 10% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 8, 10% OF  
TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 8, 30% OF TODAY'S 0Z EUROPEAN  
ENSEMBLE MEAN CENTERED ON DAY 8, 10% OF YESTERDAY'S 12Z EUROPEAN ENSEMBLE MEAN  
CENTERED ON DAY 7, 10% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8, AND  
10% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 8  
 
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  
GOOD AGREEMENT AMONG THE PREDICTION TOOLS, OFFSET BY MODERATE TO HIGH SPREAD  
AMONG THE COMPONENT ENSEMBLE MEMBERS.  
 
8-14 DAY OUTLOOK FOR DEC 08 - 14 2017  
 
DURING THE WEEK-2 PERIOD, THE FORECAST CIRCULATION PATTERN IS VERY SIMILAR TO  
THE FORECAST FOR THE 6-10 DAY PERIOD. DUE TO GOOD MODEL CONTINUITY, FORECAST  
CONFIDENCE REMAINS HIGH THAT THIS ESTABLISHED PATTERN WILL RESULT IN MUCH  
COLDER TEMPERATURES FOR THE CENTRAL AND EASTERN U.S. DURING WEEK-2. THE GFS  
ENSEMBLE MEMBERS CONTINUE TO INDICATE THAT THE ARCTIC OSCILLATION (AO) INDEX  
WILL BECOME MORE NEGATIVE WITH TIME AS FORECAST POSITIVE 500-HPA HEIGHT  
ANOMALIES ARE PROMINENT OVER THE HIGHER LATITUDES OF THE NORTHERN HEMISPHERE  
DURING EARLY DECEMBER.  
 
THE TEMPERATURE OUTLOOK DURING WEEK-2 IS BASED ON TELECONNECTIONS UPON THIS  
LARGE 500-HPA HEIGHT ANOMALY CENTER, ALONG WITH GUIDANCE FROM THE DYNAMICAL AND  
STATISTICAL TOOLS. BELOW NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF THE  
CENTRAL AND EASTERN CONUS. THE HIGHEST PROBABILITIES OF BELOW NORMAL  
TEMPERATURES ARE FORECAST ACROSS THE TENNESSEAN AND OHIO VALLEYS WHERE  
STATISTICAL TOOLS HAVE A STRONG SIGNAL. TEMPERATURE TOOLS VARY ACROSS THE  
WESTERN U.S., BUT IN GENERAL A WARMING TREND IS EXPECTED UNDERNEATH FORECAST  
ABOVE NORMAL HEIGHTS. FORECAST SOUTHEASTERLY FLOW CONTINUES TO FAVOR ABOVE  
NORMAL TEMPERATURES ACROSS CALIFORNIA AND THE SOUTHWEST.  
 
THE HIGHEST PROBABILITIES OF BELOW NORMAL PRECIPITATION ARE INDICATED ACROSS  
NORTHERN CALIFORNIA AND THE PACIFIC NORTHWEST, BASED ON THE HIGH AMPLITUDE  
RIDGE ALOFT AND STRONG SUPPORT FROM STATISTICAL AND DYNAMICAL PRECIPITATION  
TOOLS. THE LONGWAVE PATTERN ALOFT AND THE FLOW AT THE SURFACE FLOW ARE EXPECTED  
TO CHANGE LITTLE FOR ALASKA DURING WEEK-2. THEREFORE, ENHANCED ODDS FOR ABOVE  
NORMAL TEMPERATURES AND PRECIPITATION ARE LIKELY TO CONTINUE THROUGH WEEK-2  
ACROSS SOUTHERN AND WESTERN ALASKA.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 10% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 10% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 11, 10% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 11, 30% OF  
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, 20% OF YESTERDAY'S 12Z  
EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10, AND 20% OF TODAY'S 0Z CANADIAN  
ENSEMBLE MEAN CENTERED ON DAY 11  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOVE AVERAGE, 4 OUT OF 5, DUE  
TO GOOD AGREEMENT AMONG THE ENSEMBLE MEANS.  
 
FORECASTER: Y. FAN  
 
NOTES:  
 
AUTOMATED FORECASTS ARE ISSUED ON SATURDAY AND SUNDAY. OCCASIONALLY MANUAL  
INTERVENTION IS NECESSARY TO ADDRESS QUALITY CONTROL AND CONSISTENCY ISSUES. IN  
THESE CASES, FORECASTS ARE MANUALLY DRAWN BUT A FULL DISCUSSION IS NOT ISSUED.  
 
THE NOTATION FOR THE CATEGORICAL FORECAST INDICATED ON THE MAPS IS THE SAME AS  
THAT IN THE TABLES: A-ABOVE N-NEAR NORMAL B-BELOW  
 
THE TEMPERATURE MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING WARMER (ORANGE,  
"A"), COLDER (BLUE, "B"), OR CLOSE TO (UNSHADED, "N"). HISTORICAL AVERAGE  
VALUES FOR THE CALENDAR PERIOD OF THE FORECAST (DASHES, "F"). LABELS ON THE  
SHADED LINES GIVE THE PROBABILITY (> 33%) OF THE MORE LIKELY CATEGORY (B OR A).  
PROBABILITY OF N IS ALWAYS < 40%.  
 
THE PRECIPITATION MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING WETTER (GREEN,  
"A"), DRIER (TAN, "B"), OR CLOSE TO (UNSHADED, "N"). HISTORICAL MEDIAN VALUES  
FOR THE CALENDAR PERIOD OF THE FORECAST (DASHES, "INCHES"). LABELS ON THE  
SHADED LINES GIVE THE PROBABILITY (> 33%) OF THE MORE LIKELY CATEGORY (B OR A).  
PROBABILITY OF N IS ALWAYS < 40%.  
 
IN THE SOUTHWEST AND OTHER CLIMATOLOGICALLY DRY REGIONS - THERE WILL BE A  
GREATER THAN 33.3% CHANCE OF NO PRECIPITATION AND OCCASIONALLY EVEN A NORMAL  
(I.E. MEDIAN) VALUE OF ZERO - ESPECIALLY DURING THE DRY SEASONS. IN SUCH CASES  
A FORECAST OF NEAR NORMAL IS EFFECTIVELY A FORECAST OF LITTLE OR NO  
PRECIPITATION.  
 
THE CLIMATE PREDICTION CENTER USES 1981-2010 BASE PERIOD MEANS FOR  
TEMPERATURE...PRECIPITATION...AND 500-HPA HEIGHTS AS REFERENCE IN THE CLIMATE  
OUTLOOKS.  
 
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON  
DECEMBER 21  
 
ANALOGS TO THE 5 DAY MEAN OBSERVED PATTERN CENTERED 3 DAYS AGO (D-3)  
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE  
INCLUDE THE 5 DAY PERIODS CENTERED ON THE FOLLOWING DATES:  
19621124 - 19861127 - 19511128 - 19981125 - 19821214  
 
ANALOGS TO THE 7 DAY MEAN OBSERVED PATTERN CENTERED 4 DAYS AGO (D-4)  
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE  
INCLUDE THE 7 DAY PERIODS CENTERED ON THE FOLLOWING DATES:  
19861126 - 19621123 - 19881130 - 19601118 - 19631125  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 06 - 10 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B B OREGON A B NRN CALIF A B  
SRN CALIF A B IDAHO N B NEVADA A B  
W MONTANA A B E MONTANA A B WYOMING A B  
UTAH A B ARIZONA A B COLORADO N B  
NEW MEXICO B A N DAKOTA N N S DAKOTA N B  
NEBRASKA N B KANSAS B B OKLAHOMA B B  
N TEXAS B A S TEXAS B A W TEXAS B A  
MINNESOTA B B IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B A WISCONSIN B B  
ILLINOIS B B MISSISSIPPI B A MICHIGAN B N  
INDIANA B B OHIO B N KENTUCKY B N  
TENNESSEE B A ALABAMA B A NEW YORK N A  
VERMONT N A NEW HAMP N A MAINE A A  
MASS N A CONN N A RHODE IS N A  
PENN B A NEW JERSEY B A W VIRGINIA B A  
MARYLAND B A DELAWARE B A VIRGINIA B A  
N CAROLINA B A S CAROLINA B A GEORGIA B A  
FL PNHDL B A FL PENIN B A AK N SLOPE A A  
AK ALEUTIAN A B AK WESTERN A A AK INT BSN A A  
AK S INT A A AK SO COAST A A AK PNHDL A A  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 08 - 14 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A B OREGON A B NRN CALIF A B  
SRN CALIF A B IDAHO A B NEVADA A B  
W MONTANA A B E MONTANA A N WYOMING A B  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA A A S DAKOTA A N  
NEBRASKA A B KANSAS A B OKLAHOMA B B  
N TEXAS B B S TEXAS B B W TEXAS N B  
MINNESOTA B B IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B B WISCONSIN B B  
ILLINOIS B B MISSISSIPPI B B MICHIGAN B N  
INDIANA B B OHIO B B KENTUCKY B B  
TENNESSEE B B ALABAMA B B NEW YORK B N  
VERMONT B N NEW HAMP B N MAINE N N  
MASS B N CONN B N RHODE IS B N  
PENN B B NEW JERSEY B B W VIRGINIA B B  
MARYLAND B B DELAWARE B B VIRGINIA B B  
N CAROLINA B B S CAROLINA B B GEORGIA B B  
FL PNHDL B N FL PENIN B N AK N SLOPE A N  
AK ALEUTIAN A N AK WESTERN A A AK INT BSN A N  
AK S INT A A AK SO COAST A A AK PNHDL A A  
 
LEGEND  
TEMPS WITH RESPECT TO NORMAL PCPN WITH RESPECT TO MEDIAN  
A - ABOVE N - NEAR NORMAL A - ABOVE N - NEAR MEDIAN  
B - BELOW B - BELOW  
 
THE FORECAST CLASSES REPRESENT AVERAGES FOR EACH STATE. NORMAL  
VALUES - WHICH MAY VARY WIDELY ACROSS SOME STATES - ARE  
AVAILABLE FROM YOUR LOCAL WEATHER SERVICE FORECAST OFFICE.  
 
FOR ADDITIONAL INFORMATION SEE MESSAGE FXUS06 KWBC - ON AWIPS AS  
PMDMRD.  
 

 
 
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